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A NEW METAl* A lecture has been delivered by Professor Odling at the Royal Institution on the new metal, Gallium." The professor said that the nu i ber of kinds of matter known to chemists, which they have not succeeded in decomposing, but can trace undecowposed through distinct series of combinations is sixty-four. These have been roughly classified into metals, semi-metals, and non-metals, the first class being considerably the j most numerous, and the several classes merging gradually into one another. The latest known of the non-metallic elements is bromine, which was discovered in 1826 by the eminent French chemist, recently deceased, M. Balard. Within the ll'st twenty years, however, five new metallic elements have been discovered, being at the average rate of one new element every four years while some evidence of the identification also of yet a sixth new metallic element has recently been put on record. But the latest known of the fully made out new elements is gallium, which was first recognised by M. I ecoq de Boisbau- dran in the autumn of the year 1875, and so named by him in honour of tiue land of its dis- covery, France. Like its four predecessors made known within the last twenty years, gallium was discovered by the process of spectrum analysis, applied in this instance m a special manner con- trived by the ingenuity of M. de Boiabaudran himself, long eminent as a spectroscopist. The spec- trum of gallium is characterised by two marked violet lines, the less refrangible of them being especially brilliant. Hitherto the new metal has been recog- nised only in certain varieties of zinc-blende, that of Pierrefitte in the Pyrenees having furnished the chief portion of gallium hitherto obtained from any source whatever—nearly half a ton of this ore having been employed by M. do Boisbaudran to furnish the dozen grains or so of metal wherewith he has been able to establish the leading properties of the element. In its appearance gallium manifests a general resemblance to lead, but is not so blue tinted or quite so soft, though it is readily malleable, flexible, and capable of being cut with a knil e. Like lead again, and unlike zinc, gallium is not an easily volatile metal. Unlike lead, however, it acquires only a very slight tarnish on exposure to moist air, and undergoes scarcely any calcination at a red heat. The specific gravity of gallium is a little under six, that of aluminum being 2 6, that of zinc 7-1, and that of lead 114. A most remarkable property of gallium is its low melting- point. It liquefies completely at 86 deg. F., or below the heat of the hand; and, still more curiouslv, when once melted at this temperature, it may be cooled down even to the freezing-point of water without solidifying, and may be kept unchanged in the liquid state for months. Indeed, in the original communication of its discovery to the French Academy, it was described as a new liquid metal, similar to mercury but on touching with a fragment of solid gallium a portion of the liquid metal in this state of so-called sur-fusion it at once solidifies. Unlike lead, again, gallium is a highly crystalline metal, its form being that of a square octa- hedron. In its chemical habitudes the rare element gallium shows the greatest analogy to the abundant element aluminum. In particular it forms a sort of alum not to be distinguished in its appearance from ordinary allum, but containing oxide of gallium in- stead of oxide of alumnium or alumina.


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